Telephone system



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R. L STOKELY TELEPHONE SYSTEM Filed Aug. 3, 1954 7 Sheets-Sheet l N liq IIVVE/VTOR A. LSTOKKLV A TTOR/VEV Feb 4, w fi IR. L. STOKIELY TELEPHONE SYSTEM Filed Aug. 3, 1934 7 Sheets-Sheet 2 INVENTO/P R. L 5 TONE L V ATTORNEY Feb 4 @360 R. L, STOKELY TELEPHONE SYSTEM Fil g- 5, 1934 '7 Sheets-Sheet 4 3.5 k 3* mww mzwss m 4 W360 R. L. STOKIELY TELEPHONE SYSTEM Filed Aug. 3, 1934 7 Sheets-Sheet 5 [NI/ENTOR RLSTOKELV w w, mIn FEWII WMI 3 qfi W U zmwm Feb, 4 119% R. L. STQKELY TELEPHONE SYSTEM Filed Aug. 3, 1934 7 Sheets-Sheet 6 q WRGQWsQ INVENTOR R. LSTO/(ELV BY ATTORNEY wzww @150 4-,, W3, R L. STOKELY TELEPHONE SYSTEM Filed Aug. 5, 1954 7 sheets-Sheet 7 iA/l/E/VTOR R LSTUAELV A] TTOR/VEV Patented Feb. 4, 1936 2,029,683;

os'irsn stares rarest orrics TELEPHONE SYSTEM Ray L. Stokely, Floral Park, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 3, 1934, Serial No. 738,263

11 Claims. (Cl. 179-71) This invention relates to telephone systems period of conversation and may be independently and more particularly to measured service televaried, as may also the length of the initial and phone systems. succeeding periods. In. systems arranged for re- The object of the invention is to provide an ecopeated charging and also for varying the charge nomical arrangement for registering charges for in accordance with the zone in which a called telephone service in a multi-oflice system and to line is located with respect to the calling line, minimize the apparatus required for controlling it is well known to provide apparatus in an outthe necessary charging operations. going-trunk repeater for transmitting back to the In telephone systems employing impulse concharging trunk signals indicative of the zone to trolled selective switches for establishing ccnnecwhich the trunk extends; such signals may (11- 10 tions between calling and called subscribe-rs starectly effect corresponding operations of the tions, lines serving message-rate subscribers are calling subscribers meter, may be repeated by the equipped with meters, commonly referred to as charging trunk to sheet such operation, or may message registers, for registering charges for be effective to establish in the charging trunk 15 completed outgoing calls. Where line-finders the proper conditions for subsequent use in con- 15 are provided for extending calling lines to idle trolling the meter operating circuit. first selectors, these meters are usually connected In a multi-omce system arranged for zone and to the sleeve conductor of the line circuit in partimed charging, there may be both flat-rate and allel with the cut-oi? relay. Where plunger type message-rate subscribers, in which case it is necline-switches are employed, the meter for a oneessary to so arrange the charging trunks and 20 party line is usually connected to the holding conoutgoing-trunk repeaters that local or minimum ductor of the line circuit and another meter is charge calls are registered only if originated over connected to the release conductor in case the message-rate lines and so that extra charge calls line is a two-party line. Charging trunks are are registered if originated over either flat-rate included in the connections, usually between the or message-rate lines. 2 calling lines and the first selector switches, for According to this invention, such a system is controlling the operation of the associated meters. provided with charging trunks for use in regis- A well known form of such a trunk is arranged tering all calls originated over message-rate subto connect a booster-battery potential to its scribers lines, other charging trunks for use in sleeve conductor upon answer of the called subregistering extra-charge calls originated over 0 scriber, thereby operating the calling subscribers fiat-rate subscribers lines, and outgoing-trunk meter to register a charge for the call. The arrepeaters having zone and timing apparatus range-merit may such that the meter of a therein for use in registering all interoifice calls. calling line is operated once only for a completed A feature of the invention resides in the associacall, or is operated periodically during the contion of timing apparatus with a message-rate 35 tinuance of a talking connection; the meter is usucharging trunk for use in registering local calls ally operated at the beginning of each such measand in the arrangement whereby this timing apd D CL a d t Succeeding p ds Of time paratus is rendered inefiective on interoffice calls. y y 110i differ in length from t e ia A further feature resides in the provision of syn- 40 period. In multi-ofiicc systems, the meter of a ghronously operated timing apparatus in the 40 calling line may be operated a variable number message rate charging trunk and in t tof times as the charge for a completed call in going tmnk repeater to insure that the timing 0 n a 'J i i 1 l eucus'ldanuu Wlth the zone within. which the called apparatus m the chargmg trunk does not cause,

neat r r a 9* F *abefi t f to caning Ialse operation of the subscribers meter on inter- 4 Ir sai'uh a system 18 also arranged for repeated Omce Cans charging, the number of meter operations for A the initial period of conversation is varied ach drawings Whlch a part of thls 5136.01- cording to the zone, and the number of meter ficLanOn represent a telephone m l a? fer Succeeding period during both flat-rateand message-rate subscriberslmes,

which a talking connection is maintained may in Whlch the mventlon 1S embodled' The mven' 50 3.156. be a igd a ggoyding 30 the. 29113 which tion is not in its application to the specific the called station is located. The number of arrangements h wn and other applications of meter operations for a succeeding period of conthe invention will readily occur to one skilled in versation may be the same as, or different from, the art.

5:; the number oi meter operations for an initial, Referring to the drawings, Fig. l is a partial trunking layout of a multi-office telephone system;

Fig. 2 shows in an office O-I, a calling subscribers station A, a line-finder LF-l, a fiat-rate charging trunk CT-l, and a first selector S-l;

Fig. 3 shows in the ofiice l, a calling subscribers station E, a line-finder LF-Z, a mes sage-rate charging trunk CT-Z, and a first selector S-Z;

Fig. 4 shows a repeater R-2 in the ofiice O-i and a trunk T-2 extending to an office 0-2; Fig. 4 also shows, in office 0-2, an incoming second selector 3-6, a connector C-2 and a subscribers station D;

Fig. shows in the ofiice 0-l a second selector 5-3, a third selector 8-4, a fourth selector S-5, a connector C-I and a subscribers station C; Fig. 5 also shows in ofiice 0-l, an interrupter I for use with the repeaters and charging trunks;

Fig. 6 shows a repeater R-3 in office O-l, a trunk T-3 from office 0l to an office 0-3, an incoming second selector 8-! and a subscribers station X which may be in ofiice 0-3 or in some other office;

Fig. '7 shows a calling subscribers station H, a primary line-switch PLS, a secondary line-switch SLS, a fiat-rate charging trunk CT-3 and a first selector S-l3;

Fig. 8 shows the relative positions in which Figs. 2 to 7, inclusive, should be placed in order to form an operative arrangement.

The system shown in Fig. 1 comprises the live oifices O-l, 0-2, 0-3, 0-4 and 0-5, each of which includes subscribers lines and automatic switching equipment for use in establishing connections between calling and called lines. The system is one in which all subscribers telephone numbers comprise six digits, the first three of which serve to indicate the particular ofiice in which the subscribers line terminates. Each of the five offices shown represents a dififerent zone for rate purposes. The ofiice 0-l serves both fiat-rate subscribers and message-rate subscribers, line-finder switches being provided for extending calling lines to first selectors. A represents a flat-rate subscribers station, LF-l represents a line-fiinder, CT-l represents a fiatrate charging trunk between the line-finder LF-l and the first selector S-!; B represents a message-rate subscribers station, LF-Z represents a line-finder, (IT-2 represents a messagerate charging trunk between the line-finder LF-2 and the first selector 8-2; S-3, S-d, S-5 and C-! represent local second, third and fourth selectors and a local connector, respectively, for use in completing lccal cails; R-Z represents an outgoing-trunk repeater individual to a trunk T-2 leading to oflice 0-2 in Zone 2; R-3 represents an outgoing repeater individual to a trunk T-3 leading to oifice 0-3 in Zone 3, and I represents an interrupter for use with the repeaters and charging trunks in charging flatrate subscribers for interoffice calls and in charging message-rate subscribers for both local and interoflice calls. The office O-2 is represented by the incoming fourth selector S-fia, the connector C 2 and a subscribers station D. The office 0-3, which is a tandem ofiice, is represented by the incoming second selector 8-1, the tandem third selector 3-3, local third and fourth selectors 5-9 and S-i O, a local connector (3-3, and a subscribers station E; the tandem second selector S-8 gives access to groups of trunks leading to offices 0-4 and 0-5. The office O-4, which is in Zone 4, is represented by the incoming fourth selector S-H, connector C-4 and subscribers station F; and the office 0-5, which is in Zone 5, is represented by the incoming fourth selector S-IZ, the connector C-5 and the subscribers station G. Although not shown in the drawings, each of ofiices 0-2, 0-3, 0-4 and 0-5 includes switching equi ment, similar to that shown for office 0-l, for use in extending calling lines to first selectors and for completing local as well as incoming calls. Line switches might be employed in place of linefinders for extending calling lines to idle first selectors; a line switch trunking arrangement is shown in Fig. *7 of the drawings.

The line-finder switches LF-l and LF-Z shown in Figs. 2 and 3 are of the well known Strowger type and are each represented schematically by one set of brushes and one set of terminals. The broken lines represent portions of the line-finders which have been omitted. For a detailed description of the operation of the linefinders LF-i and LF-Z, reference may be had to Patent No. 1,711,682 issued to H. Hovland, May 7, 1929.

The selector and connector switches shown in Figs. 2 to '7, inclusive, are also of the Strowger type. These switches are each represented schematically by a set of brushes and one or two sets of terminals of their terminal banks. The broken lines represent apparatus and connections for these switches which have been omitted. For a complete description of the operation of the selector and connector switches, reference may be had to pages 53 to 65, inclusive, of the second edition of Automatic Telephony by Smith and Campbell.

The charging trunks CT-l and CT-3 are used only with fiat-rate subscribers lines and are arranged to operate the calling subscribers meter only on interoffice calls. Registration is effected upon receipt of from 1 to 5 boosterbattery pulses, from the repeater R-2 or R-3 over the sleeve conductor, when the called subscriber answers. These pulses are simultaneously relayed to operate the calling subscribers meter.

The charging trunk CT-2 is used only with message-rate subscribers lines and is arranged to charge for both local and interoflice calls. Registration on local calls is controlled by the usual polarized supervisory relay 308, whose windings are in series with the talking conductors of the trunk. When the called subscriber answers, this polarized relay operates to cause a booster-battery impulse to be transmitted to operate the calling subscribers meter. A timing device TS-l is provided for the purpose of providing repeated charging on local calls. This timing device, which measures time from the start of conversation and causes an operation of the calling subscribers meter for each measured unit period of conversation, comprises a magnet 340, contact springs 3M and 342, and a clutch (not shown) for engaging mechanically operated timing gears. Upon the energization of magnet 340, the clutch engages the timing gears for measuring a predetermined time interval at the end of which the contacts 3M and 342 are opened. The opening of contact 342 causes the release of magnet 340 permitting the timing device to restore to normal position. Contact 342 closes as soon as the device begins its return to normal, but contact 34! remains open until the device reaches normal. If the talking connection is not released by or before the end of the measured interval, the device TS! repeats its cycle of operation. For a detailed description of the construction and operation of such a timing dcvice, reference may be had to Patent No. 1,993,793, granted to E. D. Mead, March 12, 1935. Interofilce calls are metered upon receipt of booster-battery impulses transmitted from the repeater circuit and relayed to the calling subscribersmeter. When this trunk is associated with a repeater, the receipt of booster-battery impulses renders inefiective the apparatus used for charging on local calls.

The repeater R-2, associated with trunk T2 leading to the office O2, is arranged to repeat dial impulses over the outgoing trunk in the usual manner. When the called subscriber answers, the repeater transmits one, two, three, four, or five booster-battery impulses over the sleeve conductor to the charging trunk associated with the selector by which the repeater is seized. The booster-battery impulses are transmitted under control of the timing or charging switch TS-2 and their number is for each repeater, dependent upon the zone in which the outgoing trunk terminates. That is, the switch TS-2 will be wired to transmit the required number of impulses for a particular zone. Upon receipt of booster-battery impulses by the trunks CT-i, (IT- 3 or CT-ll, a circuit is closed for operating the calling subscribers meter a corresponding number of times as a charge for the initial unit period of conversation which the switch TS2 proceeds to count off under control of the interrupter I. If the conversation continues beyond this measured unit period, the calling subscribers meter is again operated under control of switch TS- 2 to charge for the additional unit period of conversation. The number of meter operations, and the length of the conversation period, will be fixed for each repeater according to the zone in which the ou'tgoingtrunk terminates and according to whether the charge is for the initial or a. subsequent period of conversation.

A table of six of the many possible charging plans which may be used for areas having five charging zones is shown in the patent to R L. Stokely, No. 1,859,941 granted May 2%, 1932. The wiring of the arcs of switch TS-2 of repeater circuit R--fl and the arcs of switch TS3 of repeater circuit R depends upon the plan employed for any particular area. The switches TS2 and TS-3 are shown wired to fulfill the requirements of Plan 1 of the aforementioned table. Accordirr to this the calling subscribers meter is operated once for each five minute period of conversation for calls to Zone 1, twice for calls to Zone 2, three times for calls to Zone 3', four times for calls to Zone 4 and five times for calls to Zone 5.

The repeater R-3 is similar circuit Rf-2 except that it is trunks employed in completing rality of offices and a variable number of impulses is ransznitted to the charging trunk circuit from the repeater, dependent on the zone in which the office of the called line is located. In order to identify th zone in which the called subscriber is located, a two-motion one-hunt red point tracer switch Z is employed. This switch operates as controlled by the impulse receiving relay oi the repeater to take a setting corresponding to the first two digits received by this relay. The first digit is repeated over the outgoing trunk to direct the incoming selector at the distant end of the trunk and is also to the repeater associated with calls toa pluefiective to elevate the tracer switch Z to a level corresponding to the digit dialed; the second digit is repeated over the trunk to effect the selection of a trunk to the ofdce in which the called line is located and is efiective to rotate the tracer switch Z to a set of terminals corresponding to the digit dialed. The tracer switch Z, associated with the repeater circuit R,3, therefore, identifies the zone in which the called subscribers line is located, so that the proper charging information can be transmitted to the charging trunk.

The operation of the system shown in the drawings will be further described by assuming the origination and completion of calls from stations A, B and H. Assume, first, that a call is originated at the flat-rate station A shown in Fig. Upon removal of the receiver at station A, the line relay Elli operates to cause the operation of an idle line-finder LF-l. The cut-01f relay is operated when the sleeve or test brush 2% of line-finder LF-i engages the test terminal of line 265 and the line-finder stops with its brushes 253d and 253i in engagement with the terminals to which the conductors of line 2H3 are connected. The calling line 255 is there by extended through the brushes of line-finder LF-l to the associated first selector Si. Holding ground potential is connected to the sleeve conductor 25? of selector S-l in usual manner to hold cut-oii relay 2% and to prevent the return of the line-finder LFi to normal. The connection of ground potential to conductor 2|? is also effective to energize the upper winding of relay Bill of trunk CT-l, but relay 26"! is marginal and its is not sutficiently energized to cause the operation of its contact.

When the first digit of the number of the subscribers station with which the calling subscriber desires connection is dialed, the selector switch S-i is directively operated in response to the dial impulses received by its line relay (not shown) to cause the selection of an idle set of terminals in the corresponchng level of the terminal bank. Assuming the selected set of terminals to be connected to the trunk to which the second selector 3-3 is connected, the dialing of the next two digits of the called subscribers number causes the selective operation of the second selector S 3 and a third selector S l. If

the called subscribers line is in oiiice 0-9, the terminals selected by switch S- l lead to a fourth selector S5; and the dialing or" the succeeding digits of the called subscribers number causes the selective operation of selector 8-5 and a connector 0-9 to complete the connection between the calling station A and the called subscribers station (3. If idle, the called station is signaled and upon removal of the receiver at station C, the talking connection is established in well known manner. The calling subscriber, being a flat-rate subscriber, is not charged for a local call. When the subscribers at stations A and B replace the receivers, the switches involved in the connection all restore to normal in the usual manner.

If the called subscribers line is in oiiice the dialing oi the first digits of the callec subscribers number causes the successive selective operation of switches S-l, S-It and 53-5, the terminals selected by switch S-d being con-- nected in to the outgoing-trunk repeater R-2 (Fig. l) associated with the trunk T-2 which terminates in cfiice 02. Upon extension of the calling line 2l5 through the brushes of line-finder LF-|, selectors S-|, S-3 and S4, to conductors 40| and 402 of repeater Rr2, the line relay 4|2 is operated. Relay 4|2 closes a circuit for operating the slow-to-release relay 4|4. Relay 4|4 connects a holding ground potential through its middle lower front contact, over conductor 4|5, through the back contact of relay 4|6, over sleeve conductor 403, through the lower brushes of switches S--4, S-3 and S-| to sleeve conductor 2 1 to hold the cut-off relay 209 and to prevent the return to normal of switches LF-|, Sl, S3 and 8-4. Relay 4|4 closes a circuit for operatng relay 4 8 and a circuit for energizing the upper winding of relay 4|1; but relay M1 is not operated by the energization of its upper winding alone. Relay 4|4 also closes a bridge across the conductors of trunk T2 to cause the operation of the line relay (not shown) of selector 8-5 in ofiice -2; this bridge is traced from conductor 45| of trunk T2 through the upper front contact of relay 4|4, back contact of relay 420, lower winding of relay 4I1, lowermost back contact of relay 4|3, lower winding of relay M9, and through the lower front contact of relay 4l2 to conductor 452 of trunk T-2. The current over trunk T-2 through the lower winding of relay 4H electromagnetically opposes the current through the upper winding of this relay so that relay 4|; does not operate. The aforementioned operation of relay 4|8 closes a circuit from battery through the winding and interrupter contacts of stepping magnet 405 of timing switch TS-Z, brush 409 and terminal I, resistance 42|, inner lower front contact of relay 4|8, over conductor |1 and through the winding of relay 500 of interrupter I to ground. The current in this circuit is not suflicient to operate stepping magnet 405 of switch TS-Z but is effective to operate relay 500 of interrupter I. Relay 500 closes a circuit for operating relay 50l. Relay 50| connects the interrupter contacts 503 to the winding of relay 502, these contacts being closed once every second for approximately one half a second. As soon after relay 50| operates as contacts 503 are closed, relay 502 operates and closes a circuit through the right winding and inner front contact of relay 50| to hold relay 50| operated independently of relay 500. As long as relay 500 remains operated, relay 502 is operated once every second to connect ground to impulse conductor 5|9.

When the last three digits of the called subscribers number are dialed, the line relay 4|2 releases and reoperates in response to each dial impulse. Being slow in releasing, relay 4 l4 remains operated during the receipt of each of these three trains of dial impulses. The release of relay M2, in response to the first impulse of each of these digits, closes a circuit for operating relay 420. Relay 420 being slow in releasing, remains operated until all of the impulses in a train corresponding to one digit have been received, the front contact of relay 420 being effective to short circuit the lower windings of relays 4 I I and 4 9 to insure the proper response of the selector and connector switches in office O-2 to the dial impulses repeated over trunk T-2 by the lower front contact of relay 4| 2. The selector S-6 and connector C2 are thereby directively advanced to complete the connection with the line 499 leading to the called station D. If the called line is idle, a ringing circuit is closed by the connector C2 to signal the called subscriber and upon removal of the receiver at station B, the connector C2 operates in well known manner to reverse the current over trunk T-2 and thereby causes the operation of the supervisory relay 4|1 of repeater P.2. Relay 4|1 closes a circuit for operating relay 4|3; and relay 4|3 interchanges the connections between the windings of relay M2 and conductors 40| and 402 so that the current is reversed over the talking conductors of trunk CT-| and the talking conductors of the calling line. Since the calling line is a flat-rate line, this reversal performs no useful function.

In operating, relay 4|1 also closes a circuit for operating relay 504 of the interrupter I; this circuit is traced from battery through the upper winding of relay 425, lower back contact of relay 422, lowermost front contact of relay 4|1, uppermost back contact of relay 422, lower back contact of relay 425, over conductor 5|5 to interrupter I, through the back contacts of relays 5|3 and 508, and through the winding of relay 504 to ground. Relay 504 operates but relay 425 being marginal does not operate at this time. Relay 504 closes an obvious circuit for energizing the right winding of relay 505. Relay 505 operates and with relay 502 operated a circuit is closed from battery through the winding of relay 506 in parallel with the left winding of relay 505, through the left front contact of relay 505, lowerback contact of relay 5| to ground at the front contact of relay 502. Relay 506 operates and relay 505 is held operated independently of relay 504 until relay 502 again releases. Relay 506 closes a circuit for operating relay 508. Relay 508 closes a circuit for operating relay 5|3, opens the operating circuit for relay 504 and connects ground through its inner upper front contact to the winding of relay 501. With relay 5|3 operated, ground is connected directly to conductor 5|5 to cause the operation of relay 425. As soon as relay 502 releases, relay 506 releases thereby opening the short circuit across the winding of relay 501 so that relay 501 operates in series with relay 508 to ground at the front contact of relay 500. The operation of relay 501 causes the release of relay 5|3. When relay 425 operates, it locks through the front contact of its continuity springs to ground at the inner lower front contact of relay 4| 4. Relay 425 closes a circuit for reoperating relay 504; this circuit is traced from battery through the lower winding of relay 425 in parallel with the winding of relay 422, through the inner lower front contact of relay 425, conductor 5|6, back contact of relay 5|2 and through the winding of relay 504 to ground. Relay 504 reoperates but relay 422 is marginal and does not operate at this time. Relay 504 causes the reoperation of relay 505. When relay 502 is next operated, relay 506 operates a second time. With both of relays 506 and 501 operated, a circuit is closed for operating relay 509; this circuit is traced from ground at the front contact of relay 505 through the front contact of relay 501, conductor 520, back contact of relay 5| 0 and through the winding of relay 509 to battery. Relay 509 connects ground at the front contact of relay 500 to the winding of relay 5|0; and, when relay 502 next releases, the release of relay 506 opens the short circuit across the winding of relay 5|0 so that relay 5|0 is operated and relay 509 is held operated to the ground at the front contact of relay 500. Relay 5|0 connects conductor 520 to the winding of relay 5H and when relay 502 is next operated, relay 506 is reoperated to close a circuit for operating relay 5||; this circuit is traced from ground through the front contact of relay 506, front contact of relay 501, conductor ductor 5l6 to operate relay 422.

' the operating circuit through the right winding of relay 505 and also opens the holding circuit through the left winding of relay 505 so that relay 505 releases. The release of relay 505 causes the release of any of relays 506, 507, 508, 509 and 5!!! ,which are then operated. Relay 5H also closes a circuit for operating relay 5l2. The operation of relay 5l2 causes the release of relay 504- and connects ground over conductor 5": to the winding of relay 422 in parallel with the lower winding ;of relay 425 to hold relay 425 operated and to cause the operation of relay 422. It is apparent that approximately two seconds elapse from the time ground is connected to conductor 5 l 5 to operate relay 425 until ground is connected to con- This time interval is introduced to prevent the operation of the calling subsc 'ibers meter, as hereinafter described, in case the supervisory relay 491 should be operated momentarily due to trunk or line busy signals.

When relay 422 is operated, as above described, it locks through the front contact of its continuity spring to ground at the inner lower front contact of relay 4M. Relay 422 closes a circuit for operating relay tit and opens the aforementioned locking circuit through the upper winding of relay 425. As soon as relay 502 again releases, relays 5i l, M2 and 425 release in succession, the current through the lower winding of relay 425 in series with the winding of relay 504 being insufficient to hold relay 425 operated. Since relay '25 starts to release while the contacts of relay iii? are being shifted, relay 425 releases soon enough to prevent reoperation of relay 504. With relay 422, operated, the next succeeding operation of relay 5% of interrupter I closes a circuit for operating the stepping relay 428 to initiate the advance of switch TS--2. The circuit for operating relay 420 is traced from ground at the front contact of relay 502, over conductor 5l9, inner lower front contact of relay 422, lowermost front contact of relay 4H, uppermost front contact of relay 422, terminal I and brush of bank 40% (each brush of switch TS-2 being normally in engagement with terminal I as shown in the drawings), lowermost front contact of relay 4I8, brush and terminal I of bank 401, inner upper front contact of relay 4l8, and through the uppermost front contact of relay 410, to the winding of relay 423. Relay 428 closes a circuit for operating magnet 405 of switch TS2; and when relay 502 disconnects ground from conductor 5H3, relay 428 and magnet 405 successively release. The release of magnet 405 advances the brushes of switch TS2 into engagement with terminal 2 of each of the banks. The advance of switch TS-Z from normal position causes the release of relay M0. The next succeeding connection of ground to conductor 55!] is effective to operate magnet 405 directly; the operating circuit is traced from conductor 5I9, through terminal 2 and brush of bank 406, lowermost front contact of relay 418, brush and terminal 2 of bank sill, through the interrupter contacts and winding of magnet 405 to battery. The magnet 4&5 releases as soon as its operating circuit is opened at its own contact without waiting for relay 502 to disconnect ground from conductor sac. With brush 401 in engagement with terminal 3, relay 420. againoperates before the ground is disconnected from conductor 5l9. The operation of relay 428 reoperates magnet 405 and when the ground is disconnected from conductor 5I9, relay 4 28 and magnet 405 release. Since terminals 2 to 51, inclusive, of bank 405 are strapped together, and terminals 2, 4, and'8 of bank 401 arestrapped together, and terminals 3, 5, l and e of-.-bank 48? are strapped together,- the switch TS--2 is advanced two steps per second under the control of relay 502 of the interrupter I and the steppingrelay 428 of switch TS-2 until the brushes of this switch are in engagement with terminal l0.- Relay 500 releases as soon as switch TS-2 has advanced beyond position 0 unless this relay is held operated by some other repeater to which it is common. Thereafterthe circuit for operating stepping relay 428 is traced through strapped terminals iii to 20, inclusive, and brush of bank 48? and through the brush and strapped terminals E0 to 20, inclusive, of bank 406 over conductor E0 to the interrupter contacts 5I4. Since the contacts 5E4 are closed once every thirty seconds for approximately half a second, relay 428 and magnet 40% are operated and released once every thirty seconds to advance the brushes of switch TS2 step-by-step until these brushes are in engagement with terminal 2| at which time an interval of approximately and not less than five minutes has elapsed since the switch was moved out of normal position. When the brush of bank 409 reaches terminal 2|, relay 5% of the interrupter I reoperates if not already operated. The next succeeding operation of relay 502 of interrupter I after brush 40? engages terminal 2! causes the operation of relays 429 and 430; the circuit for operating these relays is traced from ground at the front contact of relay 562 of interrupter I over conductor 5| 9, through the inner lower front contact of relay 422, lowermost front contact of relay 4H", uppers most front contact of relay 422, terminal 2| and brush of bank 405, lowermost front contact of relay M8, brush and terminal 2l of bank 401, th nce through the winding of relay 429 and through the winding of the slow-to-release relay 430 to battery. Relay 422 locks to ground at the lowermost front contact of relay 422 and connects ground to terminal 20 of bank 400. Relay 430 extends its operating ground through its front contact and the uppermost front contact of relay M8 to operate stepping relay 428 and relay 428 closes the circuit for operating magnet 405. When ground is again disconnected from conductor 5H3, relays 430 and 428 release; and the release of magnet 405 advances the brushes of switch TS2 from terminal 2| to terminal 22. As soon as ground is again connected to conductor hit, a circuit is closed over conductor 5I9 through the inner lower front contact of relay 422, lowermost front contact of relay 4H, uppermost front contact of relay 422,'terminal 22 and brush of bank 455, lowermost front contact of relay 4 l 8, brush and terminal 22 of bank 401, and through the back contact and winding of magnet 405 to battery. Magnet 405 opens its operating circuit and-the release of magnet 405 advances switch TS2 to normal.

The operation of relay 422, effective, as above described to initiate the advance of switch TS2, was also-effective to cause the operation of relay 4,55 beforethe switch advanced out of position I. If the trunk T-2,' with which the repeater R-2 is associated, extends beyond the first zone, relay 465 is reoperated oneor more times during the advance of switch TS2 to position l0. Since the trunk T2 extends into Zone 2. terminal 3 of bank 408 of repeater R2 is connected to ground as shown in Fig. 4. If the trunk T2 extended into Zone 3, terminals 3 and of bank 408 would be connected to ground; if trunk T2 extended into Zone 4, terminals 3, 5 and 1 of bank 408 would be connected to ground; and if the trunk T2 extended into Zone 5, terminals 3, 5, 1 and 9 of bank 408 would be connected to ground. Relay M6 is reoperated each time the brush 408 encounters a grounded terminal. Since it was assumed that office O-2 is in Zone 2, only terminal 3 of bank 408 is shown connected to ground, so that relay M6 is operated a second time when the brushes of switch TS2 are in position 3 and is not again operated unless the talking connection is maintained for more than five minutes, in which case the switch TS-2 is again advanced as hereinafter described.

Each time that relay 4|6 operates, the sleeve conductor 403 incoming to the repeater R2 is disconnected from conductor M5 and the positive pole of booster-battery is connected through lamp 426 and the lower front contact of relay 4|6, over sleeve conductor 403, through the sleeve brush of each of selectors S4 and S3, the sleeve brush 205 of selector S|, over conductor 2 1, through the inner upper back contact of relay 206 and the upper winding of relay 201 to the negative pole of battery and over conductor 2|1, through the uppermost back contact of relay 206, through brush 202 of line-finder LF-| and the locking contact and winding of the cut-off relay 209 to the negative pole of battery. The cut-off relay 209 is held operated and the current through the winding of marginal relay 201 is sufiicient to operate this relay. Relay 4|6 also connects ground through its upper front contact to conductor 404, thereby causing the operation of the relay 208 which is common to a plurality of charging trunks. With relays 2G1 and 208 both operated, a circuit is closed through the lower winding and front contact of relay 201 for holding relay 201 and for operating relay 206. Relay 206 locks under control of relay 208 alone and opens both the operating and holding circuits of relay 201. Relay 206 also closes a circuit through its inner lower front contact for operating relay 2|2, which is common to a plurality of lines in ofiice O-|. With both of relays 206 and 2| 2 operated, the positive pole of booster-battery is connected through lamp 2 I 4, the upper front contact of relay 206 and brush 202 of line-finder LF| to sleeve conductor 2|5 of line 2 l5, thence through front contacts of relays 209 and to the winding of meter 2||. The cut-off relay 209 is held operated and the meter 2 is operated to register one unit of charge. When relay 4|6 releases, relays 208, 206 and 2|2 release and the meter 2H releases. Each operation of relay 4| 6 is, therefore, effective to operate meter 2 and thus register one unit of charge. The connection of booster-battery to conductor 2 l1 when relay 4|6 is operated would be effective to operate meter 2| I but the connection of ground potential to conductor 403 by other selectors when hunting for an idle repeater would interfere with and possibly cause more than one operation of the meter. To prevent such interference, the operation of relay 206 disconnects conductor 2 1 from line-finder brush 202 and connects the boosterbattery through lamp 2E4 to operate the meter.

If conversation has not been completed by the end of the initial five minute period, the foregoing cycle of advancing the metering switch TS-2 is repeated. The meter 2|| is thus re-' operated one or more times at the beginning of each five minute period during which the talk ing connection is maintained as measured by switch TS2. On the initial revolution it was necessary that the switch advance from terminal 20 to 2| under control of interrupter contacts 554 in order to insure that the initial conversational period for which the meter was operated would not be less than five minutes. But, on succeeding cycles the switch has already been synchronized with the interrupter and it is advanced immediately from terminal 20 to terminal 2| without waiting for the ground at interrupter contacts 544; the circuit for operating magnet 405 is traced from ground at the lower front contact of relay 429 through terminal 20 of bank 439 and the back contact and winding of magnet 405 to battery.

When the connection is released by the calling subscriber, the line relay 4|2 of repeater R2 releases, thereby opening the loop across the outgoing conductors of trunk T-2 so as to release relay -4|1 of repeater R2 and the line relay (not shown) of the connector C2. The selector S-5 is thereupon immediately restored to normal in the usual and well known manner; and when the receiver is placed upon the receiver hook at the called station the connector C-2 is also restored to normal in the usual and well known manner. The release of relay 4|1 causes the release of relay M3; and the release of relay 4|2 causes the release of relay 4|4, whereby the holding ground is disconnected from sleeve conductor 4|5 so as to cause the release of the cutoff relay 209 and cause the selectors S|, 8-3 and 8-4 and the line-finder LF| to be restored to normal in the usual and well known manner. Relay 4|4 also causes the release of relays 422 and M8; the release of relay 422 causes the release of relay 429 and the release of relay 4H1 causes the return of switch TS-2 to its normal position by closing circuits for operating the magnet 405. If the switch TS2 is in any of positions 2, 4, 6, 8 or 22, the circuit for operating the magnet 405 is traced from battery through its winding and back contact, any one of terminals 2, 4, 6, 8 or 22 and brush of bank 401 to ground at the lower back contact of relay M8.

If the switch is in any of positions 3, 5, 1 or 9 to 20, inclusive, the operating circuit for magnet 405 is traced from battery through its winding and back contact, upper back contact of relay 4|8, any one of terminals 3, 5, 1 and 9 to 20 and brush of bank 401, to ground at the lower back contact of relay 4| 8. With the switch in position 2|, a circuit is closed for reoperating relay 430; this circuit is traced from ground at the lower back contact of relay 4|8, through the brush and terminal 2| of bank 401, to battery through the winding of relay 430. With relay operated, the circuit for operating magnet 405 to advance the switch TS2 from position 2i to position 22, is traced from ground at the lower back contact of relay 4| 8, brush and terminal 2| of bank 401, front contact of relay 430, upper back contact of relay 413, and through the back contact and winding of magnet 405 to battery. The switch IS-2 is advanced from terminal 22 to its normal position as hereinbefore described. Relay 430 releases as soon as the brush of bank 401 leaves terminal 2|. The en iii succ ss tire trunk circuit is now normal and ready for service on another call.

If the station with which the subscriber at station A desires connection is in either of offices O3, O4 or O--5, the selector Sl is directively operated to select an idle trunk T3 in a group extending to the office O3. Since additional digits must be dialed before it is finally determined in which ofiice the called line is located, the repeater R--3 which is associated with the selected trunk T3 is provided with a two digit register switch Z, the line relay 6I2 of repeater R3 being effective to repeat the impulses over trunk Tii to control the completion of the desired connection and to repeat the first two trains of impulses to operate-the register switch Z.

Upon extension of the connection from the calling line 2E5 through the brushes of linefinder LF-l and selector Sl over conductors till and 692 to the repeater R3, the line relay M2 operates. Relay (H2 closes a circuit for operating the slow-to-release relay 614. Relay EM connects ground through its lowermost front contact and the back contact of relay BIG, over sleeve conductor 563 and through the sleeve brush 235 of selector Sl to sleeve conductor 2:! to hold the selector S! and line-finder LF| in their operated position and to hold the cut-off relay see of line 2I5 all in the usual and well known manner. With relays (H2 and 6M both operated, a bridge is connected across the conductors of trunk T3 to operate the line relay (not shown) of the incoming selector S-l to which the trunk T3 connects in ofiice 0-3; this bridge is traced from conductor 55| of trunk T-3, through the upper front contact of relay EH4, back contact of relay 62%, lower winding of relay til, lowermost back contact of relay 6E3, lower winding of relay 519 and through the lower front contact of relay M2 to conductor 652 of trunk T-3. The aforementioned operation of relay tit also closes a circuit through the upper winding of relay 5!! but the current through the lower winding of relay fill is electromagnetically opposed to the current through its upper winding so that relay 6H does not operate at this time. The aforementioned operation of relay 614 also closes a circuit for operating relay 5I8. Relay SIB closes a circuit for operating relay 5530 of the interrupter I; this circuit is from battery through the winding and back contact of stepping magnet 6% of charging switch TS--3, brush and terminal I of bank 6%, resistance 62L inner lower front contact of relay 6H3, over the conductor 5!! and through the winding of relay 5% to ground. The current in this circuit is not sufficient to operate the stepping magnet 505. The operation of relay see causes the energization of relay iiill so that ground is connected to conductor 5H3 once every second by the repeated operation of relay 5532 under control of interrupter contacts 503.

The calling subscriber continues to dial all of the digits of the called stations number, the dial impulses being repeated by the repeater R3 to control the selective operation of the selector S'! and the operation of each of the succeeding switches employed in completing the desired connection. The release of relay 5l2 in response to the first impulse of each train opens the loop across the outgoing conductors of trunk T3 and causes the operation of slow-to-release relay 620. Relay 62b short circuits the lower winding of relay 6|! and the lower winding of relay 659 to reduce the impedance across the outgoing conductors of trunk T3 during transmission of outgoing impulses, relay i529 being designed to remain operated until all of the impulses in each train have been repeated. The release of relay 6E2 also closes a circuit for energizing relay 535; this circuit is traced from ground through the back contact of relay (H2, lowermost front contact of relay 6M, rotary offnormal springs 6 38 of switch Z, through the winding of relay 635 to battery. Relay 635 locks through its right front contact and the back contact of vertical-stepping magnet 636 to ground at the back contact of rotary-stepping magnet Relay 635 closes a circuit for operating the slow-to-release relay 333 and vertical-stepping magnet 633 in series; this circuit is traced from ground at the left front contact of relay 635, through the back contact of the vertical off-normal springs 5M, winding of relay 633 and L winding of magnet 636 to battery. The energization of magnet E36 opens the aforementioned locking path for relay 635 and elevates the brushes of tracer switch Z to a position opposite the first level of the terminal bank. The

actuation of the vertical off-normal springs ii l'l when the shaft of switch Z is raised out of normal position opens the above traced operating circuit for relay and magnet 635, but a holding circuit is traced from battery through the winding of magnet 636, winding and front contact of relay 6553, lower front contact of offnorrnal springs 66?, to ground at the left front contact of relay E35. Thepurpose of locking relay 635 under control of the magnets 63% and 638 is to insure the complete operation of each of these magnets in the event that an impulse received by relay 552 is too short to cause the operation of either of these magnets. The reoperation of relay 6!! at the end. of the first imof the terminal bank. Belay sit does not release during the response of relay ES IE to dial impulses; and relay 633 remains operated until r lay 6E2 reoperates after its response to the last impulse of the digit.

When the next digit is dialed by the calling subscriber, relay EH2 again responds to repeat the impulses over trunk T3 and to rotate the brushes of tracer switch Z to a corresponding position in the selected level. The release of relay 552 in response to the first impulse of this train closes the circuit for operating relay e35 as hereinbefore described. Relay S35 locks under control of magnets 83% and 633 and closes a circuit for operating relay 53s and the rotary-stepping magnet 638 in series; this circuit is traced from battery, through the windings of magnet 38 and relay 635, back contact of relay 633, lower front contact of the vertical off-normal springs 647', to ground at the left front contact of relay 635. The operation of rotary-stepping magnet 538 causes the advance of the brushes of tracer switch Z into engagement with the first set of terminals in the selected ievel. The above men ticned holding circuit for relay 635 prevents the release of this relay until magnet 63?. is completely operated. With relay B34 operated, the winding of relay 635 is connected directly through the left front contact of relay 634 to the lowermost front contact of relay SM; relay 634 is slow in releasing and remains operated until all of the im-- pulses in the train have been received so that relay 635 is alternately operated and released .in response to each succeeding release and reopera tion of impulse receiving relay (H2. Each operation of relay 635 causes the operation of magnet 638, the brushes of switch Z being advanced step-by-step into engagement with the set of terminals which corresponds to the digit dialed. While the brushes are being rotated, relay 634 prevents the premature operation of any one of zone relays 639, Bi l 6M by disconnecting battery potential from their windings. Relay 634 releases, upon reopera-tion of relay 6l2 after receiving the last impulse of the train, thereby rendering the response of relay 652, to impulses created by further dialing, ineffective to cause the further advance of switch Z. The impulses created by the dialing of the remaining digits of the called subscribers number are, however, repeated by relay H over trunk T3 to control the completion of the connection with the called line.

The terminals 545 to which the brushes 842, 543 and 654 of tracer switch Z are advanced and which correspond to and represent the traffic route over which a connection is being extended, are distinctively connected to indicate the zone into which the traffic route extends. Each of the three terminals in a set in the bank of switch Z may be connected to ground potential or left unconnected. When relay 634 releases, after the tracer switch Z is set, battery potential is reconnected to the windings of zone relays 63%, 643, and 64 I; relay 639 operates if brush 642 is in engagement with a terminal connected to ground, relay 840 operates if brush 643 is in engagement with a terminal connected to ground, and relay GM operates if brush 34-, is in engagement with a terminal connected to ground. For the particular trunking system represented in Fig. 1, none of the zone relays will be operated for a call to Zone I; relay G39 alone will be operated for a call to Zone 2; relays and 640 will be operated for a call to Zone 3; relay 340, alone, will be operated for a call to Zone 4; and relays 640 and B ll will be operated for a call to Zone 5. The arrangement is easily modified to take care of more zones. As shown in Fig. 6, the terminals with which brushes S42 and 6&3 are in engagement are both connected to ground to indicate call to Zone 3 and relays E39 and 6:10 both operate and relay 84f remains normal.

When connection with the line 698 of the called station is completed and the called subscriber answers, the current is reversed over the conductors of trunk T--3 by the operation of a supervisory relay in the connector (not shown) in the usual and well known manner thereby causing the operation of the polarized supervisory relay 6H of repeater R--3. Relay Si? closes a circuit for operating relay (H3; relay SIS reverses the current over conductors Gel and $32 and the calling line loop. Since the call originated at a flat-rate subscribers station, the reversal of current over conductors Sill and 682 is without effect. With relay 6l3 operated, both windings of relay (H9 are included in the bridge across conduotors 65! and 6&2 thereby improving the transmission through condensers 650 during talking. The aforementioned operation of relay 6!! also closes a circuit for operating relay 504 of interrupter I; this circuit is traced from battery, through the upper winding of relay 625 of peater R3, lower back contact of relay 622, lowermost front contact of relay 611, uppermost back contact of relay 622, back contact of the continuity springs of relay conductor 5l5,

use, over through back contacts of relays 5l3 and 508, and through the winding of relay 504 to ground. Rc lay 825 is marginal and does not operate until relay 5|3 connects ground directly to conductor 5l5, the operation of relay 513 being effected as hereinbefore described. Relay 625 then locks through the front contact of its continuity springs to ground at the inner lower front contact of relay 6M. With relay G operated, the lower winding of this relay is connected, in parallel with the winding of relay $22, over conductor SL5, through the back contact of relay M2 to the winding of relay 5M. Relay 504 is thus reoperated but relay 822 is marginal and does not operate until the interrupter I functions as hereinbefore described to cause the operation of relay EIE. When relay 552 operates, it connects ground to conductor 516 to hold relay E25 and cause the operation of marginal relay 622. 822 locks through the front contact of its continuity springs to ground at relay M4. The operation of relay 622 initiates the advance of timing switch TS-E, relays El i, (H8, 628, 629, 630,

resistance 62L magnet 82 5, and banks 608, 601,

5M and 609 all bein similar in operation and function to the correspondingly numbered elements repeater R-2 in Fig. 4. The crush of bank Gill; is connected to the winding of relay tit, so that this relay is operated when relay G22 operates before the switch TS-3 moves out of normal position. Terminals 2, 4, l3 and 8 of bank 863 are connected to the contacts of zone relays E39, 640 and SM so that relay lilfi operates twice per revolution of switch TS3 for a call to Zone 2; thrice per revolution for a cafl to Zone 3; four times per revolution for a call to Zone 4; and five times per revolution for a call to Zone 5. Each operation of relay 6H5 connects ground over conductor Gil to cause the operation of register control relays such as 298 and connects the positive pole of booster-battery through lamp 625 over conductor 663, to cause the operation of relays ZD'l, 2 and H2 and meter 2H as hereinbefore described. The subscribers meter 2! is thereby operated three times for the first five minutes of conversation and three times for each additional period on the call to Zone 3. If the called line were in Zone 2, the meter would be operated twice for each five minutes of conversation as measured by switch TS-Z; if the called line were in Zone 4, the meter would be operated four times for each five minutes of conversation as measured by switch TS-3; and if the called line were in Zone 5, the meter would be operated five times for each five minutes of conversation.

If a call is originated at the message-rate subscribers station 13, the line 3'29 is extended by the operation of a line-finder LF2, through brushes 380, 30l and 3422 to the message-rate charging trunk CT-2. The selector S-Z associated with trunk CT-.'2 responds to the impulses created by the dialing of the first digit of the number of the subscriber with whom connection is desired. A local call is completed through selectors such as S3, S4, 8-5 and a connector Cl; a call into Zone 2 is completed through selectors S3, S4, a repeater R-Z, a selector S-6 and a connector C2; and calls to Zones 3, 4 and 5 are completed through a re- Relay peater Rr-3, a selector S--l and succeeding selectors and a connector in accordance with the trunking arrangement shown in Fig. 1.

The holding circuit for the cut-off relay Sill of line 326 is traced through its front contact, brush 332 of line-finder conductor 3 i 9, back contact of the continuity springs of relay M3, to sleeve conductor of selector 8- 2, thence to holding ground potential at the connector on a local call or at an outgoing repeater if the call is an interoiiice call. The timing switch TSl being normal, the winding of relay 3 is connected through the uppermost back contact of relay 3l3 and the contact of timing switch 'IS-l to sleeve conductor 329. Relay 3i i is marginal and does not operate unless and until booster-battery is connected to sleeve conductor 329 as hereinafter described.

If the call is a local call, the usual reversal of current by the operation of a supervisory relay in the connector when the call is answered causes the operation of the polarized relay 3% of trunk CT2. Relay 3538 closes a connection from the lower Winding of relay 3&9, through the front contact of relay 3GB, upper back contact of relay 3H], back contact of the continuity springs of relay 339, over conductor 322, to conductor 5E5 of interrupter I, thence through the back. contact of relay EH3, lower back contact of relay 5%, and through the winding of relay 5% to ground. Relay 5334 operates but relay 365 is marginal and does not operate at this time. Relays 56 i, 595, 50!, 532, 5iltand 588 and contacts 5G3 of interrupter I are effective as hereinbefore described to cause the operation of relay 5E3. Relay his connects conductor 5 l 5 directly to ground thereby causing the operation of the marginal relay Silt of trunk CT2. Relay 339 closes a locking circuit which is traced through the front contact of its continuity springs, contact 342 of the timing device TS--i to the holding ground potential connected to sleeve conductor 323. With relay 3% operated, the upper Winding of relay iillil and the windings of relay Sill and clutch magnet 3% are all connected in parallel to conductor 323, thence over conductor 5M5, through the back contact of relay 5&2 and winding of relay 5% to ground. Relays 3% and 5% are thereby held operated but relay 3m and magnet etc are marginal and do not operate in series with relay 5%. Relays 532, 5535, hilt, 58?, $89 and Mil now operate to measure an interval of one and one half seconds at the end of which relays 5H and 552 are operated. Relay 552 connects ground to conductor 5H5 for half a second thereby causing the operation of relay 393 and clutch magnet 343 of trunk CT-2. Relay 3H and clutch magnet ?dii are held operated independently of relay 3% through the front contact of the continuity springs of relay Sill in series with contact of timing device TS-i over sleeve conductor 323 to holding ground potential. Relay 3i?) opens the holding circuit through the lower winding of relay 389, but the holding circuit through the upper Winding of relay 3% is effective to hold relay 339 operated until relay 552 of interrupter I releases, the resistance of the winding of relay 584 (to which conductor 52% is connected when relay M2 releases) being suincient to cause the release of relay The circuit through the winding of relay see is opened soon enough by the release of relay sec to prevent the reoperation of relay 5%. Relay closes a circuit through its lowermost front contact and the lowermost front contact of relay 3&9 for energizing the lower winding of relay 3l3. In operating, relay 3&3 connects its upper winding to a front contact of relay 3M, closes a circuit for operating the meter control relay Sit and connects the positive pole of booster battery through lamp 325i and the inner lower front contact of relay tit, over sleeve conductor tie to cause the operation of meter When relay releases, relay 343 is released thereby disconnecting the booster-battery from sleeve conductor SIS and causing the release of relay tilt and meter 3H5.

The release of relay Sit prevents meter 3E5 from being held operated by the holding ground potential when relay 3i3 releases.

If the connection is released before five minutes have been measured by device TS-i, holding device are opened at the end of five minutes thereby causing the release of relay 3m and magnet S lt The release of magnet etc causes the immediate reclosure of contacts 3G2 but contacts 3M are held open until the timing device reaches its normal position thereby preventing the reoperation of magnet 3% and the reengagement of the driving clutch in any other than normal position. If the talking connection is continued beyond five minutes, the continued operation of relay 3533 causes the reoperation of relay 3G9 and the above described cycle of operations is re-' peated to cause another operation of meter 3|5 and the measurement of another five,minute interval.

If the trunk CT2 is employed in completing an interoffice connection through either one of repeaters R2 or R3, the connection of booster-battery to sleeve conductor 329 by the operation of relay tilt of a repeater R-2 or relay BIG of a repeater R-B is efiective to operate the marginal relay 3H of trunk (ET-2 and the connection of ground to conductor 404 of a repeater R2 or conductor 6% of a repeater R3 causes the operation of relay 3 i l. The operation of relay 3! l prevents the operation of magnet 34!! of timing device TSl, or causes the release of the timing device TSi if already moved off-normal as hereinbefore described. Relay 3! l closes a circuit for operating relay 3E2. Relay 3l2 looks over the sleeve conductor 329 to prevent the operation of magnet 34% when relay 3H releases; Relay 3i i also closes a circuit for operating relay Slit. Relay 3!?) looks over sleeve conductor 329 and closes a circuit through the upper winding of relay 3E3; relay 3&3 operates and closes a looking circuit to the front contact of relay 3 M. The operation of relay 5H3 causes the release of relay 3i i, connects booster-battery to sleeve conductor 3H), and closes the circuit for operating relay 316 as hereinbefore described. Since the operation of relay 3i 5 occurs while conductor 323 is connected to ground at the front contact of relay 5l2 of interrupter I, and if relays 3B8, 383 and 3H! have operated before relay 3!! is operated by boosterbattery potential, relay 3l3 will have been operated due to the energization of its lower winding as hereinbefore described. The energization of relay 3 it holds relay 3E3 operated until the booster-battery is disconnected from conductor 329. When relay M6 of repeater R2 (or relay 6 l6 of repeater R-3) releases, relays 3 l4 and 3 l3 are released but relays 3H] and M2 are held over sleeve conductor 329 by ground potential until the comiection is released. Each succeeding op eration of relay M6 (or BIG) causes the reoperation of relays 3H and 3I4 followed by the operation of relays 3|3 and 3H5 and meter 3l5. Since the operation of relay 313 connects booster-battery through lamp 326 to sleeve conductor 3l9 each time booster-battery is connected to sleeve conductor 329, the temporary connection of ground potential to the terminal with which brush 305 is in engagement by another selector cannot cause more than one operation of meter 3l5 for each operation of relay M6 (or 6I6).

When the called subscriber replaces the receiver on the receiver hook, the reversal of current through the windings of relay 308 causes its release. If the call is a local call, further advance of timing device TSI is thus prevented. When the holding ground potential is disconnected from conductor 329, relays 3| 0, 3H and 3l2 release, if operated, the line-finder LF-2 and selector S2 being restored to normal in usual manner.

To illustrate the application of the invention to a system employing line-switches in place of line-finders, Fig. 7 may be substituted for Fig. 2. The primary line-switch PLS and secondary line-switch SLS shown in Fig. 7 may be of the well known Keith type. For a complete description of the construction and operation of such switches, reference may be had to pages 44 to 50, inclusive, and pages 83 to 89, inclusive, of the second edition of Automatic Telephony by Smith and Campbell. Only the holding winding of the magnet T02 of line-switch PLS is shown. The meter 103 is provided for operation to record the charge for calls other than local calls. The line relay and plunger magnet of the secondary line-switch SLS are not shown.

Upon removal of the receiver at station H to originate a call, the line 10! is extended through its primary line-switch PLS to a secondary line switch SLS. The upper winding of relay H0 is, thereupon, connected in series with the winding of the meter 103. Relay H0 is sufficiently energized by the current in this circuit to close its lower front contact, but its upper contacts remain in their normal positions. The meter I03 is marginal and does not operate in series with the winding of relay H0. The closing of the lower contacts of relay H0 causes the operation of the secondary line-switch SLS, thereby extending the connection over trunk CT3 to the first selector Sl3. The holding ground potential, connected in well known manner to sleeve conductor H3, completes the operation of relay H0 due to the energization of its lower winding and maintains the energization of the holding winding of the magnet 102 of line-switch PLS. The complete operation of relay H0 disconnects its upper winding from the winding of meter 103 and connects the winding of meter 103 to conductor H9 of trunk CT3. Relay H5 is marginal and the energization of its upper winding when holding ground potential is connected to sleeve conductor H3 is insuflicient to cause the operation of this relay.

On a local call none of the relays in the trunk CT--3 is operated, no operation of meter 103 being required. But on an interofiice call for which a charge should be made, the operation of a relay M6 or 6H5 in a repeater R2 or R-3 through which the call is completed, causes the operation of relay H1 and connects booster-battery to sleeve conductor H3 in place of ground potential to operate relay H5. The operation of relays H5 and ii? causes the operation of relay H6. Relay H6 locks under control of relay H1 alone, causes the release of relay H5, and connects battery to sleeve conductor 1 I 9 to cause the operation of meter 103. When the relay 6 (or MS) of the repeater releases, relay H1 and meter 103 release. Each time that booster-battery potential is connected to sleeve conductor H3 by the repeater through which the connection is completed, the meter T03 is operated. Upon release of the connection the magnets of lineswitches PLS and SLS are released and relay H0 releases.

The invention is not limited in its application to the particular switching and trunking arrangements hereinbefore described and is applicable to interofiice systems employing other types of switches and different trunking schemes.

What is claimed is:

i. In a multi-oi'lice telephone system, subscribers lines, means including a charging trunk for extending a calling one of said lines to 3. called line in the same oflice, means including said charging trunk and an outgoing trunk for extending said calling line to a called line in another office, a meter for said calling line, means in said charging trunk for operating said meter, timing apparatus associated with said charging trunk for controlling said meter operating means only on local calls, and timing apparatus associated with said outgoing trunk for controlling said meter operating means on interofi'ice calls.

2. In a multi-office telephone system, subscribers lines, means including a charging trunk for extending a calling one of said lines to 9. called line in the same office, means including said charging trunk and an outgoing trunk repeater for extending said calling line to a called line in a different oflice, a meter for said calling line for registering charges for completed calls in accordance with their duration and the location of the called line, means in said charging trunk for operating said meter, timing apparatus associated with said charging trunk for controlling said meter operating means only on local calls, and timing apparatus associated with said outgoingtrunk repeaterfor controlling said meter operating means on interoihce calls.

3. In a multi-office telephone system, subscribers lines serving message-rate subscribers, message-registers for the message-rate lines, switching means for use in completing talking connections between calling and called lines, charging trunks for controlling the operation of said message-registers, one of said trunks being included in each connection, outgoing trunks for use in completing interoffice calls, timing apparatus in each of said charging trunks for measuring off periods of time during which the charging trunk is included in a talking connection, timing apparatus for each of said outgoing trunks for measuring oft periods of time during which the outgoing trunk is included in a talking connection, means in said charging trunk controlled by the timing apparatus therein for operating the calling subscribers message-register at the beginning of each measured period of time during which the charging trunk is included in a talking connection, and means in said charging trunk controlled by the timing apparatus of an associated one of said outgoing trunks for rendering the timing apparatus of said charging trunk ineffective and for operating the calling subscriber's register at the beginning of each measured period of time during which said outgoing trunk is included in a talking connection.

4. In a multi-oiiice automatic telephone systern. subscribers lines, automatic switches for use in completing a talking connection between a calling line and a called line, a meter for said calling line, a charging trunk included in the connection between the calling line and the first of said switches, said charging trunk comprising means for counting ofi intervals of time as long as the talking connection is maintained, meter operating means,.and means for rendering said meter operating means operatively effective at the beginning of each of such intervals, an outgoing-trunk repeater in the connection between the first of said switches and said called line, said repeater comprising means for counting off intervals of time as long as the repeater is connected in an established talking connection, means for transmitting one or more charging impulses at the beginning of each of such intervals, means for varying the number of impulses transmitted in accordance with the office in which the distant end of the trunk terminates, and means in said charging trunk responsive to charging impulses received from said repeater for controlling said meter operating means in accordance with said impulses.

5. In a multi-ofiice telephone system, subscribers lines, means including a charging trunk for extending a calling one of said lines to a called line in the same office, means including said charging trunk and an outgoing trunk for extending said calling line to a called line in another ofiice, a meter for said calling line, means in said charging trunk for operating said meter, timing apparatus associated with said charging trunk for controlling said meter operating means on local calls, timing apparatus associated with said outgoing trunk for controlling said meter operating means on interoffice calls, and means in said charging trunk for rendering the timing means therein ineffective to control said meter operating means on interoffice calls.

6. In a multi-ofiice' telephone system, subscribers lines, means including a charging trunk for extending a calling one of said lines to a called line in the same ofiice, means including said charging trunk and an outgoing trunk for extending said calling line to a called line in another office, a meter for said calling line, means in said charging trunk for operating said meter, timing apparatus associated with said charging trunk for controlling said meter operating means on local calls, and timing apparatus associated with said outgoing trunk for controlling said meter operating means on interoffice calls, the timing apparatus in said charging trunk being synchronized with the timing apparatus in said outgoing trunk to prevent the control of said meter operating means by the timing apparatus of the charging trunk on interoffice calls.

'7. In a multi-omce telephone system, flat-rate subscribers lines and message-rate subscribers lines, a meter for each or" said lines, means for completing connections between calling and called lines in the same office, means including a group of outgoing trunks for completing connections from both flat-rate and message-rate lines to called lines in another office, meter operating means arranged to operate the meter of a calling flat-rate subscribers line only on interoffice calls, and meter operating means arranged to operate the meter of a calling message-rate subscribers line on both local and interoffice calls.

8. In a multi-office telephone system, flat-rate subscribers lines and message rate subscribers lines, a meterfor each of said lines, charging trunks for use in completing calls originated by flat-rate lines, other charging trunksfor use in completing calls originated by message-rate lines, outgoing trunks for use in completing calls originated by both fiat-rate and message-rate lines, timing means in each of said message-rate charging trunks for controlling the operation of the meters of calling message-rate lines on local calls, and timing means associated with each of said outgoing trunks for use in controlling the operation of the meters of calling flat-rate lines and the operation of the meters of calling message-rate lines.

9. In a multi-office telephone system, messagerate subscribers lines, fiat-rate subscribers lines, a meter for each of said lines, charging trunks for use in controlling the meters of said messagerate lines, other charging trunks for controlling the meters of said fiat-rate lines, means including said charging trunks for extending connections from calling to called lines, outgoing trunks for use in completing interoffice calls, apparatus for each of said outgoing trunks operative in response to the completion of a talking connection for measuring off intervals of time during which the talking connection is maintained and for transmitting metering signals at the beginning of each of said intervals, means in each of said charging trunks, both flat-rate and mes sage-rate, responsive to metering signals received from any one of said repeaters for efiecting corresponding operations of the meter of an associated calling line, timing means in each of the message-rate charging trunks for measuring of! intervals of time during which the trunk is included in a completed talking connection, and means in each of the message-rate charging trunks for controlling the operation of the meter of an associated calling line, said last mentioned means being under the control of the timing apparatus in the charging trunk on a local call and under the control of the timing apparatus of the outgoing trunk on an interoffice call.

10. In a multi-office telephone system, subscribers lines, means including a charging trunk for extending a calling one of said lines to a called line in the same ofiice, means including said charging trunk and an outgoing trunk for extending said calling line to a called line in another ofiice, a meter for said calling line, means in said charging trunk for operating said meter,

timing apparatus associated with said charging l trunk for counting oii conversational-unit periods of time during which a talking connection is maintained through said charging trunk on local calls, and timing apparatus associated with said outgoing trunk for counting oif conversational-unit periods of time during which a talking connection is maintained over said outgoing trunk, said meter operating means being under the control of said timing apparatus in the charging trunk on local calls and under the control of said timing apparatus in the outgoing trunk on interofiice calls.

11. In a multi-ofiice telephone system, subscribers lines, means including a charging trunk for extending a calling one of said lines to a called line in the same office, means including said charging trunk and an outgoing trunk for extending said calling line to a called line in another ofiice, a cut-off relay for said calling line connected to the sleeve conductor of said charging trunk, means for connecting a holding ground potential to said sleeve conductor to operate said cut-off relay, conversation-timing apparatus associated with said charging trunk, conversationtiming apparatus associated with said outgoing trunk, a meter for said calling line, a source of meter operating potential in said charging trunk, a multi-contact relay common to said lines and having a set of contacts individual to each of said lines, means controlled on local calls by said timing apparatus of the charging trunk and on interomce calls by said timing apparatus of the outgoing trunk for temporarily connecting said meter operating potential to said sleeve conductor in place of said holding ground potential and for simultaneously causing the operation of said multi-contact relay, the operation of said multicontact relay being effective to connect said meter to said sleeve conductor in parallel with said cut-off relay while said meter operating potential is connected to said conductor.

RAY L. STOKELY. 

